This invention relates to removal of offshore structures after the useful life of the structures in their original offshore location. More particularly, the invention is directed to a method of removing piling-anchored offshore platforms in an environmentally acceptable manner.
Many drilling and/or production platforms used in drilling for and/or producing oil and gas in shallow or moderately deep water are anchored to the seabed by large steel pilings which extend into the seabed and which support the platforms. Such platforms have a finite useful life, and after that are preferably removed to a new location or scrapped. In either event it is necessary to separate the platform from its anchoring pilings
Environmental regulations require that pilings be cut at a specified depth, typically about 5 meters, below the seabed.
Various cutting techniques have been utilized, with varying degrees of success. The most common piling cutting technique uses explosives to sever the pilings at the required depth. Environmental and regulatory groups have objected to this technique as harmful to marine life.
Non-explosive cutters using mechanical cutters or abrasive fluid jets have been tried, but are costly and difficult to use, particularly in deeper waters.